1. Field of the Invention
The present invention relates to a method and apparatus for sorting pieces of waste of materials having different properties.
2. Description of the Prior Art
According to conventional sorting methods, the pieces are moved along a substantially straight conveying path, their different properties, including color, if desired, are sensed along the conveying path, and the pieces are then removed at respective discharge stations, dependent on the sensed properties of the materials of the pieces.
Particularly if the pieces are disposable containers, such as bottles, cans or the like, problems arise because the round pieces frequently change positions along the conveying path as they move therealong, or the pieces may jump up as they are fed to the conveying path. This may lead to an erroneous discharge of the respective pieces, thus considerably reducing the quality of the sorting. However, a precise sorting according to the different properties of the materials of the pieces is of decisive importance for the quality of any new product to be made from the sorted pieces, particularly, for example, in the recycling of synthetic resin materials.
U.S. Pat. No. 4,946,046 discloses an apparatus for sorting seeds according to color. This apparatus comprises a convex conveying path defined by the peripheral wall of a hollow drum. The peripheral wall surface has recesses for holding the seeds therein by the force of gravity, and the color of the individual seeds held in the recesses is sensed. Blow nozzles are arranged in the interior of the drum, and the recesses holding the seeds have holes through which the nozzles may blow out discolored seeds. This arrangement can be used for pieces of like size, such as seeds, which correspond to the size of the recesses. Pieces of varying sizes cannot be securely held in the recesses. Furthermore, the apparatus is extremely costly.